There is a specialization of AnyConversion<std::string>::toCorbaType for TAO
implementation use while serializing a std::vector<std::string> into a string
sequence. This specialization is not choosen in some cases if the string
sequence element is given by reference. I only observe this issue recently with
msvc 2008 and 2010. I didn't have this problem when I have submitted this
functionality (see commit 506a183a9a3c0e6c3a9220e6333812c1a04bc0c5).

Moreover in TAO implementation a string sequence element is a kind of smart
pointer to the serialized string (a char*), so I think it's intended to be pass
by value.